3 Answers
3

Short Answer, YES; Long Answer, YES YES

The word in Greek is Metanoeo which means: To change ones mind. The word repent in Hebrew is Nacham which means to: to be sorry, be moved to pity, have compassion.

Repentance is a state of mind, of sorrow over your actions.

Now that we understand the word's definition we need to understand the context that the word is used in. Here in the old testament is one verse, of many, that defines repentance.

Ezekiel 18:30 NKJV

“Therefore, you Israelites, I will judge each of you according to your
own ways, declares the Sovereign LORD. Repent! Turn away from all your
offenses; then sin will not be your downfall.

Repentance is to turn away from all of your offenses, to turn away from sin.

So you can see that repentance is a mindful state of abhorrence to the things that you have done. The bible says that we need to prove this mindful state by our actions. Have a look:

Acts 26:20 niv

First to those in Damascus, then to those in Jerusalem and in all
Judea, and to the Gentiles also, I preached that they should repent
and turn to God and prove their repentance by their deeds.

Your turning away from sin is proven by what you do.

Repentance is: Having a changed mind that turns you from the things that you were once doing in order that you may do the opposite.

What does God say about Repentance?

We are commanded to repent of our sins.

Job 36:10 niv

He makes them [his children] listen to correction and commands them to repent of
their evil.

Acts 17:30 niv

In the past God overlooked such ignorance, but now he commands all
people everywhere to repent.

What does Jesus say about Repentance?

Here we see Jesus talking about the final judgement, he's giving us insight into what He will say and do on that day.

Matthew 7:21-23 (NKJV)

21 “Not everyone who says to Me, ‘Lord, Lord,’ shall enter the kingdom
of heaven, but he who does the will of My Father in heaven. 22 Many
will say to Me in that day, ‘Lord, Lord, have we not prophesied in
Your name, cast out demons in Your name, and done many wonders in Your
name?’ 23 And then I will declare to them, ‘I never knew you; depart
from Me, you who practice lawlessness!’

We know that sin is lawlessness. Christ is literally saying that if you practice sin He will have nothing to do with you, you did not know Him and He did not know you. In this next verse you see Jesus commanding us to repent, He does this constantly throughout his testimony on this earth.

Matthew 4:17 (NIV)

From that time on Jesus began to preach, "Repent, for the kingdom of
heaven is near."

Luke 3:3

He went into all the country around the Jordan, preaching a baptism of repentance for the > forgiveness of sins.

It's interesting what Luke says here, a baptism of repentance FOR the forgiveness of sins. If we put this altogether with what else we have learned so far, we see that if we turn from our sins then God will be faithful and forgive us for those sins.

So if this is true, then the opposite should also be true. If we continue to sin then we will go to Hell? Let's see if what the Bible says.

Hebrews 10:26-27 (NIV)

26 If we deliberately keep on sinning after we have received the
knowledge of the truth, no sacrifice for sins is left, 27 but only a
fearful expectation of judgment and of raging fire that will consume
the enemies of God.

Finally God says that He stands FIRM on this very statement. He will not change His mind.

2 Timothy 2:19 (NIV)

19 Nevertheless, God’s solid foundation stands firm, sealed with this
inscription: “The Lord knows those who are his,” and, “Everyone who
confesses the name of the Lord must turn away from wickedness.”

Assurance of salvation as it relates to repentance

1 John 1:6-76 NIV

If we claim to have fellowship with him yet walk in the darkness [evil], we
lie and do not live by the truth. 7 But if we walk in the light [love], as he
is in the light, we have fellowship with one another, and the blood of
Jesus, his Son, purifies us from all sin.

If you continue to sin then the truth [Holy spirit, God, Jesus] is not in you.

1 John 2:4-5 NIV

The man who says, "I know him," but does not do what he commands is a
liar, and the truth is not in him. But if anyone obeys his word, God's
love is truly made complete in him.

If you say that you know God, but you continue to sin, not loving as you were commanded, then you are a liar and [Holy spirit, God, Jesus] is not in you.

Repentance is a struggle against the desires of your flesh

Revelation 2:19

I know your deeds, your love and faith, your service and perseverance,
and that you are now doing more than you did at first.

You will not be perfect right away, you will go through a lot of discipline and correction from God, so that you may produce more and more fruit throughout the days of your life. Persevere in your repentance.

Hebrews 10:36

You need to persevere so that when you have done the
will of God, you will receive what he has promised.

gotquestions.org/repentance.html states "To repent, in relation to salvation, is to change your mind in regard to Jesus Christ". This seems to be totally different from what you posted. Do you agree with that page? If so, how does this post reconcile with that?
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PacerierAug 2 '14 at 23:45

Yes, it's a requirement... or better, a precondition. In order to be saved, you have to accept Jesus sacrifice. But for this, you have to realize that this sacrifice was necessary. And for that, you have to realize... your sin.

Now... you could accept your sin ("Yup, bad stuff")... without leaving it. Makes sense? Don't think so, but people may be wanting to see it that way. Here, the gospel (and that means, Jesus) is quite clear: you cannot accept the gift of life but keep to your old ways. Doesn't work that way (and it should be quite obvious why... would you forgive someone if you knew he'd keep on doing what you just forgave him?)

As to the second part of your question: it is both. It is a single act, when you accept Jesus as your Savior and Lord. And it's a sort-of ongoing process... because, being imperfect sinners, we always fall. So, we have to pick ourselves up and continue (stumbling) on. That means repentance every time we fall.

But beware: do not dwell on sin. No matter how big and nasty it was, it is already forgiven. Jesus died once, he doesn't die again every time you need forgiveness. The longer you dwell on it, the longer the enemy can keep you away from God. Doing whatever it was is bad enough, but staying away from God because of it makes it worse. He wants us close, and be close to us, always.

Standard Disclaimer: I do not speak for any tradition, denomination, or what-have-you. Authority? Ask God to show you if what I say is true. Then, either he confirms or he doesn't. That's all. (Dang, why doesn't this thing not have support for a signature or similar...)

Feel free to edit or propose edits, but I generally don't hunt for verses before I post, sorry. AFAIK, quotations are not required (unlike on skeptics.SE). And some of this isn't "scriptural", it's just using my experience and my God-given brains.
–
Jürgen A. ErhardAug 29 '11 at 19:58

3

Why should Christianity.SE be held to a lower standard of excellence when it comes to contending for our faith than anyone on Skeptics.SE?
–
Caleb♦Aug 30 '11 at 9:01

1

Verses are not required, but if your answer claims to represent Christianity and other Christians contest the basis of your answer you are going to have to be able to defend it. Purely personal viewpoints that do not claim to speak for any larger group are not encouraged and subject to extra scrutiny and hence the need for references. You don't want just any hobo coming along and telling other people about what you believe when he doesn't know the same Jesus you do, do you?
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Caleb♦Aug 30 '11 at 9:09

Kudos to @JonathonByrd for his answer! I would just like to add a verse that I recently stumbled on in Luke:

JUST AT that time there [arrived] some people who informed Jesus about
the Galileans whose blood Pilate had mixed with their sacrifices.
And He replied by saying to them, Do you think that these Galileans
were greater sinners than all the other Galileans because they have
suffered in this way?
I tell you, No; but unless you repent (change
your mind for the better and heartily amend your ways, with abhorrence
of your past sins), you will all likewise perish and be lost
eternally.
Or those eighteen on whom the tower in Siloam fell and
killed them--do you think that they were more guilty offenders
(debtors) than all the others who dwelt in Jerusalem?
I tell you,
No; but unless you repent (change your mind for the better and
heartily amend your ways, with abhorrence of your past sins), you will
all likewise perish and be lost eternally.
Luke 13:1-5 - Amplified

The moment someone truly accepts Jesus, they have remorse for their sins, and they are saved. Once we have our salvation, we cannot lose it (John 10:28-29). However, you will continue to sin, so therefore you should continuously repent for those sins. Not necessarily for salvation, but to have a better relationship with the Lord.

Also, when we deliberately sin, and don't repent to God (maybe because we feel ashamed and/or don't really feel sorry because we keep doing it), we become more numb to the sin and it brings less conviction and takes us farther from God each time we do it.